Cervical incompetence, often termed cervical insufficiency, describes the inability of the cervix to maintain its function during the second and early third trimester, resulting in miscarriage or premature birth. Various conditions and iatrogenic causes (drugs, surgery) have shown to play a role in the pathogenesis of this condition. Clinical criteria, information regarding previous pregnancies and transvaginal ultrasonography are necessary during the diagnostic workup.
Under physiological circumstances, the cervix possesses a crucial role in maintaining the fetus within the uterine cavity throughout the entire pregnancy, but in the setting of cervical incompetence, defined as a painless dilation and shortening of the cervix during the second trimester, the cervix is unable to perform its respective function  . As a result, the expulsion of a live fetus during the second (or sometimes third) semester is the main clinical presentation of cervical incompetence, frequently resulting in miscarriage or sometimes in premature birth    . The pathogenesis is yet to be revealed, but several risk factors have been established. Firstly, a significant ethnic predisposition toward African-American women is observed when compared to Caucasian women . Secondly, several conditions are associated with an increased risk for cervical incompetence, including polycystic ovarian syndrome (PCOS), use of diethylstilbestrol (DES), previous surgery (termination of pregnancy, repeated cervical dilation, cone biopsy, and several other procedures) or trauma (during vaginal or cesarean delivery), as well as Ehlers-Danlos syndrome and uterine abnormalities    . Cervical incompetence is completely asymptomatic in the majority of cases prior to sudden fetal expulsion, while vaginal spotting or bleeding, abdominal or lower back pain, and discharge are seen in some women prior to the event .
Various reports from different parts of the world have emphasized the markedly increased rates of cervical incompetence than previously anticipated  . Thus, this condition is hypothesized to be a rather important cause of premature delivery, but of miscarriage and fetal loss as well, which is why the diagnosis should be made as early is possible. A history of repeated pregnancy loss or preterm births is one of the first and most important elements that could be identified during history taking . Secondly, the presence of any of the mentioned risk factors is necessary during workup, suggesting that a thoroughly obtained patient history is a vital step in order to raise clinical suspicion toward cervical incompetence, especially because an asymptomatic course is seen in almost all women. On the other hand, transvaginal ultrasonography has shown to be of pivotal benefit in predicting the ability of the cervix to maintain normal pregnancy  . Studies indicate that preterm birth or fetal expulsion is much higher if cervical shortening ≤15 mm and its dilation is observed, while protrusion of fetal membranes into the cervical canal might also be suggestive of cervical incompetence  . In addition, fetal fibronectin (fFN), and interleukin-6 in amniotic fluid are mentioned by certain authors as potentially useful markers in predicting preterm delivery . However, the information obtained during history taking remain crucial for the diagnosis of cervical incompetence, meaning that physicians must maintain a high index of suspicion in women with previous preterm deliveries and miscarriages.